The study, the first to examine the long-term effects of childhood diet on behaviour, found that 10-year-olds who ate confectionery daily were more likely to have been convicted of a violent crime by the time they were 34.

Researchers said that giving sweets to children as a “quick reward” may prevent them from learning to wait for results and instead teach them to become impulsive.

Earlier this year a Scottish Government report found almost half of all children in Scotland were eating sweets or chocolates once a day or more often.

The new research suggests that improving children’s diets could help reduce violent behaviour.

Lead researcher Dr Simon Moore, of Cardiff University, said: “Our favoured explanation is that giving children sweets and chocolate regularly may stop them learning how to wait to obtain something they want. Not being able to defer gratification may push them towards more impulsive behaviour, strongly associated with delinquency.

“It is about the way rewards are administered in their developmental environment and how that teaches them to make decisions in the future.

“If they are aggressive and get a sweet as a way of diverting that behaviour, that will nurture a more violent disposition.”

The study was based on data from the British consort study, which focused on 17,415 babies born in April 1970, and monitored them at seven further stages of their lives to assess their health, education and social and economic circumstances.

Two-thirds (69%) of those who were violent at the age of 34 had eaten sweets and chocolate nearly every day as 10-year-olds, compared with 42% who were not violent.

The study, published in the British Journal of Psychiatry, said the link between eating sweets and chocolate every day and aggression in adulthood was “significant”, even when they took into account other factors.

Dr Moore said that the study was launched after a wider project with young offenders highlighted the fact that violent youngsters who showed impulsive behaviour also had “appalling” diets.

The researchers said that children who regularly eat confectionery could develop a taste for chocolate and sweets and, if they continue to eat unhealthy food as an adult, their behaviour could be affected by the additives within the products.

They said: “Childhood confectionery consumption may nurture a taste maintained into adulthood, exposing adults to the effects of additives often found in sweetened food, the consumption of which may also contribute towards adult aggression.

“This association needs further attention. Targeting resources at improving children’s diet may improve health and reduce aggression.”

The Food Standards

Agency has asked UK manufacturers and retailers to voluntarily remove six artificial colours, mainly red and yellow, from their products by the end of this year after scientists at Southampton University warned that the additives were having “deleterious effects” on children.

Their 2007 study showed many children can become more impulsive, inattentive and hyperactive after consuming artificial food additives found in drinks, sweets and processed foods.

‘Youngsters who showed impulsive behaviour also had appalling diets’